In this article we report an experimental investigation of the far-infrared
properties of several nonlinear crystals, LiNbO3, LiTaO3, ZnTe and CdTe. U
sing Terahertz Time-Domain Spectroscopy (THz-TDS) we have measured the comp
lex frequency response, i.e. both index of refraction and absorption up to
3 THz (100 cm(-1)) for the electro-optic crystals at room temperature. The
single Lorentzian oscillator model is used to describe the aquired data. Ad
ditional resonance features are observed, especially in the II-VI compounds
.